This disclosure relates generally to the field of wellbore drilling operations ancillary to actions that lengthen (drill) the wellbore. More specifically, the disclosure relates to method for providing operating guidance to drilling unit operating personnel for optimum speed of movement of a drill string in and out of a wellbore (“tripping”), and for collecting and comparing actual tripping measurement data to benchmark tripping data to evaluate and improve efficiency of particular drilling unit operating personnel (“crews”).
Wellbore drilling operations include activities ancillary to drilling the wellbore, including, e.g., tripping a drill string (i.e., assembly of drill pipe segments as “stands” and/or “joints”) out of the wellbore and back into the wellbore for the purposes, among others, of changing drill bits or other drilling tools, setting a conduit (e.g., a casing or liner) in the wellbore and circulating drill cuttings out of the wellbore along its entire length.
Tripping may be speed constrained by reason of hydrostatic fluid pressure changes in the wellbore caused by removal of the drill string from the wellbore or insertion of the drill string into the wellbore. Fluid displacement by such movement of the drill string, combined with viscous effects of the drilling fluid (“mud”) in the wellbore may cause corresponding decreases or increases in the hydrostatic pressure of the mud. If the hydrostatic pressure is increased by excessive speed “tripping in” (i.e., moving the drill string into the wellbore), it is possible to exceed fracture pressure of one or more exposed formations in an uncased part of the wellbore (called “surge”). Conversely, decrease in hydrostatic pressure caused by excessive speed “tripping out” (i.e., removing the drill string from the wellbore) may result in the hydrostatic pressure being reduced below the formation fluid pressure of some exposed formations (called “swab”). Either of the foregoing may result in a wellbore pressure control emergency situation.
It is well known in the art how to calculate increases and decreases in hydrostatic pressures caused by tripping if the drill string configuration is known and the mud properties (e.g., density, viscosity) are known.
Tripping may also be speed constrained by reason of shock and vibration of the drill string as it moves through the wellbore. If shock and vibration limits are exceeded for certain drill string components, then they may be susceptible to failure during drilling operations.
It is desirable to communicate such information to a drilling unit operating crew in an easy to use form so that their operating procedures can be guided and improved. It is also desirable to accumulate statistical information over a wellbore and in some cases compare to benchmark operating procedures from other wellbores in order to improve drilling unit operating crew performance.